The effect of a multi-component school-based social network intervention on children's body mass index: a four-arm intervention study.

Objective: Schools are considered an important setting for stimulating healthy weight. The current study is unique in examining effects of a multi-component school-based social network intervention on children's body mass index z-scores (zBMI).Methods: Four schools were randomly allocated to one of four conditions: a social network intervention using influence agents focusing on water consumption, physical activity, a combination of the two, or a passive control condition. Participants included a total of 201 6- to-11-year-old children (53.7% girls; Mage = 8.51, SDage = 0.93). At baseline, 149 (76.0%) participants had a healthy weight, 29 (14.8%) had overweight and 18 (9.2%) had obesity.Results: Linear mixed effect models indicated that a multi-component school-based social network intervention targeting both water consumption and physical activity was most effective in decreasing children's zBMI.Conclusion: This study suggests that schools can contribute to the intervention of childhood obesity-even without involving the parents-by targeting both children's water consumption and physical activity through influential peers, but more research is needed to identify mechanisms of change.

Effects of a non-eating confederate on food intake do not persist for everyone over time when people are left alone: An exploratory study.

An extensive body of research has established that eating with others can have inhibitory effects on food intake. Recent findings suggest that these effects may (partly) persist over time when the eating norm is no longer enforced. To gain more insights into the persistence of effects of a live non-eating stranger, the main aim of the present study is to explore how food intake of young women changes as a result of previous exposure to a non-eating confederate (i.e., adult stranger). To address this aim, an experiment was conducted in which 64 young women, aged 17 to 26 (M = 19.81, SD = 1.95), were given access to chocolates at two different time points. First, participants were all paired with a non-eating stranger (i.e., confederate). Afterwards, half of the participants remained with the non-eating stranger (i.e., together-together condition), while the other half was left alone with the food (i.e., together-alone condition). Results indicated that participants who were left alone increased their intake on average, although raw data revealed interesting individual differences. In contrast, most of the participants who remained with the non-eating stranger did not increase intake. Participants in an ad hoc added control condition (i.e., no exposure to a non-eating confederate; alone-alone condition; n = 26) showed food intake similar to participants in the together-alone condition after they were left alone. Our findings suggest that if intake behaviors are too extreme and divergent from the desire to eat as much as possible, women may, on average, only adhere to these behaviors in the presence of others.